import {-# SOURCE #-} DsExpr ( dsExpr, dsLet )
import {-# SOURCE #-} Match ( matchSinglePat )
-import HsSyn ( Stmt(..), HsExpr(..), GRHSs(..), GRHS(..) )
-import TcHsSyn ( TypecheckedGRHSs, TypecheckedPat, TypecheckedStmt )
-import CoreSyn ( CoreExpr, Bind(..) )
+import HsSyn ( Stmt(..), HsExpr(..), GRHSs(..), GRHS(..), HsMatchContext(..) )
+import TcHsSyn ( TypecheckedGRHSs, TypecheckedPat, TypecheckedStmt, TypecheckedMatchContext )
+import CoreSyn ( CoreExpr )
import Type ( Type )
import DsMonad
import DsUtils
+import Unique ( Uniquable(..) )
import PrelInfo ( nON_EXHAUSTIVE_GUARDS_ERROR_ID )
-import Unique ( otherwiseIdKey, trueDataConKey, hasKey, Uniquable(..) )
-import Outputable
+import TysWiredIn ( trueDataConId )
+import PrelNames ( otherwiseIdKey, hasKey )
\end{code}
@dsGuarded@ is used for both @case@ expressions and pattern bindings.
dsGuarded :: TypecheckedGRHSs -> DsM CoreExpr
dsGuarded grhss
- = dsGRHSs PatBindMatch [] grhss `thenDs` \ (err_ty, match_result) ->
+ = dsGRHSs PatBindRhs [] grhss `thenDs` \ (err_ty, match_result) ->
mkErrorAppDs nON_EXHAUSTIVE_GUARDS_ERROR_ID err_ty "" `thenDs` \ error_expr ->
extractMatchResult match_result error_expr
\end{code}
In contrast, @dsGRHSs@ produces a @MatchResult@.
\begin{code}
-dsGRHSs :: DsMatchKind -> [TypecheckedPat] -- These are to build a MatchContext from
- -> TypecheckedGRHSs -- Guarded RHSs
+dsGRHSs :: TypecheckedMatchContext -> [TypecheckedPat] -- These are to build a MatchContext from
+ -> TypecheckedGRHSs -- Guarded RHSs
-> DsM (Type, MatchResult)
-dsGRHSs kind pats (GRHSs grhss binds (Just ty))
+dsGRHSs kind pats (GRHSs grhss binds ty)
= mapDs (dsGRHS kind pats) grhss `thenDs` \ match_results ->
let
match_result1 = foldr1 combineMatchResults match_results
-> DsMatchContext -- Context
-> DsM MatchResult
-matchGuard (ExprStmt expr locn : should_be_null) ctx
+-- See comments with HsExpr.Stmt re what an ExprStmt means
+-- Here we must be in a guard context (not do-expression, nor list-comp)
+
+matchGuard [ResultStmt expr locn] ctx
= putSrcLocDs locn (dsExpr expr) `thenDs` \ core_expr ->
returnDs (cantFailMatchResult core_expr)
+ -- ExprStmts must be guards
-- Turn an "otherwise" guard is a no-op
-matchGuard (GuardStmt (HsVar v) _ : stmts) ctx
+matchGuard (ExprStmt (HsVar v) _ _ : stmts) ctx
| v `hasKey` otherwiseIdKey
- || v `hasKey` trueDataConKey
+ || v `hasKey` getUnique trueDataConId
+ -- trueDataConId doesn't have the same
+ -- unique as trueDataCon
= matchGuard stmts ctx
-matchGuard (GuardStmt expr locn : stmts) ctx
+matchGuard (ExprStmt expr _ locn : stmts) ctx
= matchGuard stmts ctx `thenDs` \ match_result ->
putSrcLocDs locn (dsExpr expr) `thenDs` \ pred_expr ->
returnDs (mkGuardedMatchResult pred_expr match_result)